Speaker Repair... getting started

[wrl]

Ok, so I just picked up an 18 inch woofer at a surplus shop in town. Trouble is... it doesn't work. I removed the dust cap and found that there is no connection between the input and the voice coil... (problem!). What I was wondering is if I can simply reattach these wires (once I find them) to the voice coil, or if I need to do other things to get it to work.

Also, I can't seem to get the voice coil out through the dust cap hole so I would likely have to remove the cone. I can post pics if people think that this can be repaired. No other visible damage can be seen (i.e. burns... suspension and surround are all fine)

So, in conclusion... do you think this can be repaired??

Thanks,
-Wes


BTW, none of my last 5 posts have been answered + I'm pretty sure someone knows the answers... before I start bumping all of them to the front page... if anyone wants to take a look, it would be appreciated!

 

[SY]

Some photos might help.

When you say that there's no connection between the terminals and the voice coil, how did you determine this? Are the wires still physically there? Is the coil itself intact? Are the ends of the coil accessible?

 

[wrl]

ok, photos to come

There is one VERY short lead on the coil, and the other is under some tape. The coil looks in good shape, but I will need to look closer if I can get it out of the speaker. As for the wires from the input, I can follow them up until the go into the cone... then they dissappear so further inspection is required.

I'll post pictures soon, but I guess what I was wondering is if there are any special procedures for disecting the darn thing so that in the event it can be saved, I don't ruin it. Like I said everything else (cone, suspension) appears to be in good shape so I would like to salvage these if possible.

Thanks,
Wes

 

[tom1356]

Well, if it will keep you from bumping things i'll take a shot this.
To get the voice coil out you need to remove the cone as they are attached.
Start by removing the outer gasket material where the screw holes are. Then you need to free up the spider down near the magnet a good exacto type knife will probably be your best bet.
Chances are slim you will be able to fix it short of a doing a full recone job, but it is a good learning experience.
Once you get it apart try to unwind a turn of the voice coil.
Good luck.

 

[wrl]

Just to be clear... remove basically means cut out (i.e. ruin) right?
Will it be hard to find new materials to rebuild? Also, the cone and voice coil are NOT connected...hence not working

Thanks for the replies guys. I'm normally extremely happy with the help I've gotten from this forum. Just been sitting home for the holidays (bored) + watching my other threads gather dust got me antzy to get started on something.

Thanks,
Wes

 

[SY]

You want to try and keep the cone intact, but the surround and (usually) the dust cap are pretty easy to trash and replace.

Pictures GOOD.

 

[tom1356]

Just to be clear... remove basically means cut out (i.e. ruin) right?
Will it be hard to find new materials to rebuild? Also, the cone and voice coil are NOT connected...hence not working

Thanks for the replies guys. I'm normally extremely happy with the help I've gotten from this forum. Just been sitting home for the holidays (bored) + watching my other threads gather dust got me antzy to get started on something.

Thanks,
Wes

Unless you posses an amazing ability with an exacto knife, yes you wil most definitly ruin it.
re-aligning the voice coil on the cone wouldn't be an easy job even if you got it all apart perfectly.
What kind of driver is it?
There are replacement cones avilable for some drivers try a google search for reconers.

 

[Vikash]

Just to be clear... remove basically means cut out (i.e. ruin) right?
Will it be hard to find new materials to rebuild? Also, the cone and voice coil are NOT connected...hence not working

Doesn't have to be ruined. The surround and spider are glued down and should be removable - maybe after you get it started with a sharp knife. You should have a chance of detatching the cone without damaging it too much and re-attaching/gluing it again later.

Finding materials is a bit more difficult and depends on what you're after and where you are. I know it's not easy/cheap to find stuff in the UK, but it may be a possibility where you are. Use our friend google. I remember it returning a few re-coning places in the states last time I searched.

Cone and VC not connected? Someone may have already had a go it.

I think that if the VC is not damaged (windings appear intact and uniformly wound) then it's worth a stab. Can you tell if you can unwind a little and attach some wire to the two ends? Get your multimeter out and make sure the winding is ok.

 

[Centauri]

Complete cone can be removed intact with a bit of patience. First you have to soften the glue under the surround and spider - acetone in an eye-dropper is good for this, let it soak in. Using a SHARP narrow chisel, you can carefully separate the suspensions from the speaker frame - try not to stretch anything.

When reassembling, use some strips of plastic cut from ice cream container as spacers between the voice coil and pole piece to keep it centred.

Cheers

 

[JOE DIRT®]

wrl......in repsonse to your first post.....if the voice coil magnetic wire has been unattached that is the first sign that the driver has been overdriven.......saving grace is that to repair or replace the voice coil you only need to remove the dust cap......the voice coil in typical drivers are wound on a paper "former" as it is called.....they are typically glued in place and can be removed with a heat gun or a damn good hair dryer with patiance......if removed then it is critical that it is centred exactly

 

[Centauri]

they are typically glued in place and can be removed with a heat gun or a damn good hair dryer with patiance

Begging to differ, but you will find that in most speakers the hole in both cone and spiders are exact size of coil former (which is smaller diameter than outside of coil) and the whole three are epoxied together (this point being subjected to most stress and heat) and therefore nearly impossible to separate, and definitely not possible through dust cap.

Wes,
If cone and coil are separated, then my guess is spider is still attached to coil and cone has torn, thereby snapping voice coil leads. The flexible lead in wires are usually soldered to voice coil wires on top of cone and sealed with blob of glue - a little acetone will clear that. If you can actually find ends of voice coil wires, and there is enough to solder to, then insert previouly mentioned plastic strips to hold everything, repair solder connections and epoxy the whole lot together (being careful to to glue the spacer strips) - will require patience!!

Cheers

 

[JOE DIRT®]

my interpretation was that there was a break to the terminal output and not the tinsel lead to the cone....ultimatley for that connection to break was due some thermal or mechanical stress and thus it being a 18 inch driver my gut feeling is that it was driven pretty hard

 

[Bull]

reply

Usually a dead speaker, is a speaker with no damage u can see when it's essembled--- is a burnt out voice coil.
And a few cases of bass drivers i've found,the surround and cone won't move at all when pressed with the hand-- which has always been a burnt voice coil.
So if the speaker moves when u push you hand lightly down on the cone then the voice coil is not usually burnt.
So to detemine after this whether the voice coil or former is damaged in any way.Put your ear close to the centre of the cone, whilst u push your hand down on the cone and any scraping noises will be a damged vc/former.

Also the voice coil is sometimes attached to the tinsel leads by a thin wire between the voice coil and tinsel leads,if this thin wire between the tinsel lead and voice coil has snapped,the voice coil can appear to look fine whilst u wonder why it doesn't work.

To remove the surround and spider without damaging it you can buy some solution called debonder which softens up and breaks down glue bonds.
Maplin Electronics sell it by Rite-Lok Debonder and is cheap to buy.
The stuff is toxic
wear glothes,and use in well ventilated areas,ie outdoors, but NOT corrosive.